Infrared remote control technology

General info

With most pieces of consumer electronics, from camcorders to stereo equipment, an infrared remote control is usually always included.Video and audio apparatus, computers and also lighting installationsnowadays often operate on infra-red remote control.The carrier frequencyof such infra-red signals is typically in the order of around 36 kHz. The control codes are sent in serial format modulated to that36 kHz carrier frequecy (usally by turning the carrier on and off).There are many different coding systems in use, and generallydifferent manufacturers use different codes and different datarates for transmission."IR" stands for infrared. Infrared light is invisible since its frequency is below that of visible red. Otherwise, it is like any other light source, operating under the same laws of physics. In most cases, the IR signals are produced by an LED source. TV remotes send commands only one way, in a low-speed burst for distances of up to 30 feet. They use directed IR with LEDs that have a moderate cone angle to improve ease-of-use characteristics. The IR signal sent out by those devices is generally modulated to around38 kHz carrier using amplitude shift keying (carrier on or off). The data rate send is generally in ra range of 100-2000 bps. Please note that there are some IR systems which use other frequencies and other modulation systems.IR transmit and receive systems are inexpensive and are generally reliable. However, interference from other IR sources can be a minor issue. Interference can come from IR remote controls, IR audio systems (these broadcast an IR signal continuously) or other IR sources. Interference can also be caused by other light sources such as fluorescent lights (the ballast can cause IR interference). Sometimes some electronic ballasts powered light can cause interferenceproblems. In order to avoidany interference with this kind of equipment, the operating frequencyof all electronic ballasts has to be chosen so that problemsin the 36 kHz frequency area are out of the question. Many existing IR systems modulate the IR light at around 36-40 kHz (this is the frequency of the IR carrier and should not to be confused with the actual frequency of the IR light itself). The possibility of interference is more likely around the 40 kHz frequency. One way to limit interference is to use higher IR carrier frequencies. Some IR systems now use carrier frequencies into the megahertz region.Generally infrared remote controls are a 32-40 kHz modulated square wave for communication. This square wave is then send to IR transmitter (IR LED). The carried frequency is amplitude modulated by the data, usually full on/off type modulation. The data rate is typically in 50-1000 bit/s range depending on the system used. Usually the tranmitter part is constructed so that the transmitter oscillator which is driving the infrared transmitter LED can be turned on/off by applying a TTL voltage on the modulationcontrol input (the signal that goes here is usually serial datafrom remote control keyboard decoding IC). On the receiver side a photodiode takes up the signal. The integrated circuit inside a typical receiving chip is sensitive only around a specific frequency in the 32-40 kHz range. The output is the demodulated digital input, just what wasused to drive the transmitter. Usually this kind of receivers work os that when IR the carrier is present, this output is high. When no carrier is detected, the output is low.This type of circuits can usually transmit a 1-3 kHz digital signal through infra light. When trying to receive IR signals, leave demodulation to one of the special IC's/modules ment for this and deal with the data only.The free air IR data transmission, IR remote control aswell as the most optoelectronic sensors and lightbarrier systems work with a wavelength between870nm and 950nm. The system described above is not the only one IR remote system in use, it is just the most commonly used one. Asystem that use unmodalated signals of a one kHz or 100 kHz (and several other frequencies) exist as well.

Inside TV Remote Control
- The remote control's job is to wait for you to press a key, and then to translate that key-press into infrared (pronounced "infra-red") light signals that are received by the TV. When you take off the back cover of the control you can see what is inside it.
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Programming your Universal Remote Control
- Lost your manual? Can't figure out how to change the settings on your universal remote control? This webpage is a list of IR remote controller programming resources plus other online locations that offer help on programming various remote controls.
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IR repeater circuits are remote control signal extenders. They can be used for example topick up remotecontrol's signals and send them trough a long cable to a IR-transmitter inthe other end of the cable, that would send the remotecontrol's signals to the IR signal recieving equipment that is placed in another room.

Build a remote controller

The Next to Minimal InfraRed Transmitter for PC
- The Next to Minimal InfraRed Transmitter for PC was designed for a specific purpose: to invoke the 'Easy Startup Menu' of a SONY AV equipment, whose remote control is missing. No soldering iron, nor a oscillator was available - only one spare part infra red LED and a couple of hours. The solution was obvious - the infra red LED could be inserted to the parallel port, and both the carrier and modulator produced by software.
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Transmitter and receiver combinations for remote controlling

12 Channel IR Remote With Relay Board
- This kit comprises a commercial 14-button remote control unit and a 12 channel relay board. This makes it very simple to add infrared remote control to any project or existing equipment. This page has a document that has complete details, including schematic and theory of operation.
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Misc circuits

Basic Infrated TX-RX
- The transmitting section of this infrared tx-rx is unusually simple but it works rather well: the infrared LED pulses at a frequency of 160Hz and its range, with its receiver, is between 2 and 4m depending on the transformer used and the setting of the 100k pot.
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Micro power 40 KHz burst laser diode driver
- laser tag or simulated combat games can use this circuit to send short bursts of modulated laser light at the opponent's vest, equipped with a matching light receiver, operates from three 1.5v cells (4.5v) that should provide enough energy for about 200,000 shots, pdf file
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Universal IR Controller for a PC
- This simple circuit allows you to record any IR remote control signal on your PC, and then play it back. This is particularly useful if you want to control appliances such as TVs, VCRs, CDs etc. from your computer. The device simply connects to the parallel port of your PC. You can also use this circuit to analyze the waveform from any IR remote control. This circuit was originally published in Electronics Australia, September 1998.
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Serial port controlled infrared transmitter with PIC
- This is a programmable infrared (remote control) transmitter, which can be controlled from a PC serial port. It is capable of sending many remote control formats, including the Philips RC-5 standard. The controller will accept commands on the serial port. Settings are: 19200 bps, 8 bits, no parity, 1 stopbit, no flow control (XON/XOFF or RTS/CTS). Commands consist of hex coded bytes and must be written on the port as ASCII characters separated by space, terminated by ENTER (ASCII char 0d). You can use a terminal emulator program to test out the circuit. This document has also information how to analyze IR remote control protocol signals.
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Receivers

How to build a simple but cool IR (Infra Red) receiver
- This is a step by step guide to build a serial infrared receiver for your computer, with many pictures and detailed instructions. This circuitry allows you to control your computer with a simple remote, like the one you already use for your TV-set. You can use LIRC for Linux or WinLIRC, the windows port as the control software.
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Universal Infrared Receiver
- a small (1x2x1 inch) device that allows you to control your PC with the remote from your TV, VCR, CD or Stereo, based on PIC 12C509, connects to RS-232 port, also version for PIC 16C84
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Universal Infrared Receiver
- This is an UIR compatible infrared remote controller receiver that plugs to PC serial port. It is implemented using IR remote receiving module and PIC16F84. This device can be used for example with Girder software to control your PC.
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Girder
- program that receives the codes from the Universal Infrared Receiver (UIR) or the IRman and translates them into actions in your Windows computer
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LIRC
- Linux software package that allows you to decode and send infra-red signals of many (but not all) commonly used remote controls
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PC Remote Control
- This software that lets you remotely control your computer from the serial port (RS-232). This software works with many IR receivers, including commercial and homebuilt design. This software works also with IrDA-compliant transceiver module with ASK/TV Remote compatibility.
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WinLIRC
- Windows equivalent of LIRC, the Linux Infrared Remote Control program which allows reception of IR signals with very simple receiver circuit. WinLIRC allows you to transmit and receive standard infrared remote control signals. This allows you to control your computer using almost any standard infrared remote control. It also allows your computer to control other equipment which uses these signals (stereo equipment).
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Product information

Misc

Infrared Head Phones
- Using this low-cost project one can reproduce audio from TV without disturbing others. In place of a pair of wires, it uses invisible infrared light to transmit audio signals from TV to headphones.
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Control protocols

Decoding IR remote controls
- There are at least two international standards which are used by remote controls to encode the commands, the RC5 and RECS 80 code. This documenent has informtion on them and how to receive IR remote controller signals.
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